Reference may be made to the following U.S. Pat. Nos. of interest: 3,535,021; 3,767,287; 3,817,634; 3,901,603; 3,910,680; 3,912,369; 3,927,930; 3,938,878; and 4,053,207.
In some instrument applications, it is necessary to measure the magnitude (sometimes referred to herein as the "degree") of polarization of light containing multiple components with different orientations of electric field. For practical reasons, the polarization in the case of fluorescent light normally is described by measuring the intensity of light at two orientations, Z and Y, and calculating the magnitude or degree of polarization, P, as the ratio of (I.sub.z -I.sub.y)/(I.sub.z +I.sub.y), or rearranged as (R-1)/(R+1), where R=I.sub.z /I.sub.y, and wherein I.sub.z is the intensity of light with the electric field vector parallel to the electric field vector of the exciting light, and I.sub.y is the intensity of light with the electric vector perpendicular to the electric vector of the exciting light.
In the prior art, there exists accurate, but relatively expensive instruments wherein the measurement of I.sub.y and I.sub.z can be performed by passing the light through a polarizer to a detector and measuring one component such as I.sub.y, and then rotating the polarizer 90.degree. and measuring the second component, I.sub.z. In such current instruments, the operator must normally rotate the polarizer in order to obtain the two measurements. An alternative is to rotate the polarizer automatically using a mechanism such as a stepping motor, however, such mechanisms add to the cost and detract from the reliability of such an instrument. An alternative technique is to use two detectors simultaneously, one with a polarizer oriented to pass Z-polarized light, and the second detector with a polarizer oriented to pass Y-polarized light. Such a system adds the expense of an additional detector, polarizer, and other optics and would not be consistent with an attempt to provide a desired low cost, yet accurate and reliable instrument for measuring the magnitude of polarization.